Inductive contactless energy transfer systems are particularly suitable for environments where gas or dust ignition hazard occurs, such as mines, fuel stations and chemical laboratories, as well as those environments where the use of direct connections is impracticable, such as implants or rotating components.
Contemporary DC/DC resonant converters comprise a number of inductive elements which, depending on the applied resonant circuit, can additionally be magnetically coupled or magnetically non-coupled. The cylindrical shape of inductive elements is not suited for optimal utilization of mounting surface area. Where a plurality of inductive elements is used, the distances between inductive elements should be increased in order to avoid undesired couplings. In such case integrated inductive elements may advantageously be used.
A prior art inductive module known from the U.S. Pat. No. 7,598,839 comprises N inductors and N+1 core elements. Each magnetic element has a cavity to situate a winding. These magnetic elements are stacked in such a manner that the back of a preceding magnetic element closes the magnetic circuit of a subsequent magnetic element.
A structure described in the U.S. Pat. No. 7,525,406 comprises a plurality of coupling and non-coupling inductive elements and at least one closed magnetic circuit composed of adjacent magnetic elements, which have penetrated grooves for electric current conductors along an X-axis and a Y-axis orthogonal to the X-axis. The current conductors situated along the same axis provide mutual inductance whereas there is no coupling between mutually orthogonal current conductors.
From the U.S. Pat. No. 7,242,275 there is known a variable inductive element immune to high voltage between a control circuit and the controlled inductance. This variable inductor includes two cores of a permeable magnetic material formed in the shape of the letter “E” having three legs, including a centre leg and two outer legs. The main winding is wound around the centre leg of the first core, whereas the control winding is wound around the outer legs of the second core. Both cores are separated by means of a dielectric insulating spacer. The use of an additional magnetic flux conductor is optional. The described variable inductive element is intended for use in voltage converter resonant circuits.
The aforementioned examples illustrate embodiments of integrated reactance elements and an embodiment of a controlled reactance element. These components can be used in typical DC/DC resonant converters implementations. However, the aforementioned integrated reactance elements are not entirely suitable for use in resonant converters that provide contactless energy transfer to a separate receiver. For example, a contactless energy transfer circuit is known from the Polish patent application No. P-381975. This circuit comprises a plurality of reactance elements in its transmitter part and an inductive element including a magnetic element in a portable receiver part. For the purpose of said disconnectable and contactless energy converter it is advisable to develop a specific integrated reactance module, which would include all essential inductive power elements. This module should also ensure reliable operation with open magnetic circuit, optimal energy transfer to a receiver with closed, or partially closed, magnetic circuit, and allow for correction of the resonant frequency changes caused by proximity of an inductive receiving element.
The U.S. Pat. No. 4,675,638 and the German patent application DE3802062A1 present integrated reactance modules, comprising a magnetic element and a plurality of coaxial windings of reactance power elements separated from each other with magnetic flux conductors constituting an integral part of the magnetic element, wherein all the windings of reactance power elements are situated inside the magnetic element
In an article “A magnetic coupled charger with no-load protection” by Sakamoto H et al. (IEEE Transactions on Magnetics vol. 34 no. 4, part 01, 1 Jul. 1998), pages 2057-2059, ISSN: 0018-9464) there is presented an integrated reactance module (FIG. 6), comprising a winding of reactance power elements (NM1) situated inside a magnetic element and a winding of a control circuit (NF2) situated outside the magnetic element. The winding of a control circuit is not used directly for transmitting power but only for control of the power transmission, therefore it is not a winding of reactance power element.